1. Field
The described technology relates generally to a rechargeable battery capable of maximizing an amount of an active material coated on a positive current collector.
2. Description of the Related Art
As technical developments and demand for mobile devices have increased, demand for rechargeable batteries as an energy source has also increased. For example, a cylindrical rechargeable battery includes an electrode assembly formed by spirally winding a separator and electrodes disposed on both sides of the separator together in a shape of a jelly roll, a center pin disposed in a hollow portion in the center of the electrode assembly, a case containing the electrode assembly therein, and a cap assembly closing and sealing an open side of the case.
In the electrode assembly, the electrode includes a coated region (a composite region) formed by coating an active material (a composite slurry) on a current collector and an uncoated region exposing the current collector at the end of the coated region. The uncoated region is usually positioned at both ends of the electrode assembly, is connected to the case through the negative current collecting plate, and is connected to the cap assembly through the positive current collecting plate and the lead tab.
In the cylindrical rechargeable battery having a limited volume, a positive active material often determines the cell capacity. Accordingly, to obtain a high-capacity cell, it is required that the positive active material is maximally increased. In the example of the positive electrode described above, the uncoated region where the active material is not coated on either surface of the current collector, is located at both ends of the current collector. However, only one uncoated region is connected to the lead tab, while the other uncoated region does not contribute to the cell capacity and simply occupies an inner space of the cell. In other words, the extra uncoated region decreases the capacity in the rechargeable battery of the limited volume.
To compensate for the capacity reduction, a positive electrode, where the uncoated region is not provided at both ends of the current collector, is applied. The positive electrode in this case is formed by the current collector and the coated region during the spiral-winding process of the electrode assembly. As a result, the positive electrode includes the uncoated region at the center of the electrode assembly, and the lead tab is welded to the uncoated region.
However, since the additional uncoated region is removed from the front end of the electrode assembly, the front end becomes deformed due to the thickness of the coated region and starts to push the separator. Accordingly, a short circuit may be generated in the electrode assembly.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.